1. Field of the Invention
The present invention is in the field of markers to be employed at biopsy sites to permanently mark the site, and to methods and apparatus for applying the permanent marker. More particularly, the present invention relates to a marker that is optimally adapted for marking biopsy sites in human breast tissue with permanently placed markers that are detectable by X-ray.
2. Brief Description of the Background Art
In modern medical practice small tissue samples, known as biopsy specimens, are often removed from tumors, lesions, organs, muscles and other tissues of the body. The removal of tissue samples may be accomplished by open surgical technique, or through the use of a specialized biopsy instruments such as a biopsy needle. A well known state-of-the-art instrument that is often used in connection with the practice of the present invention is known as the “vacuum assisted large core biopsy device”.
After a tissue sample has been removed, it is typically subjected to diagnostic tests or examinations to determine cytology, histology, presence or absence of chemical substances that act as indicators for disease states, or the presence of bacteria or other microbes. The above mentioned and other diagnostic tests and examinations per se are well known in the art and need not be described here. It is sufficient to note that the information obtained from these diagnostic tests and/or examinations is often of vital importance for the well-being of the patient and is used to make or confirm diagnoses and often to formulate treatment plans for the patient. As is known, obtaining a tissue sample by biopsy and the subsequent examination are frequently, almost invariably, employed in the diagnosis of cancers and other malignant tumors, or to confirm that a suspected lesion or tumor is not malignant, and are frequently used to devise a plan for the appropriate surgical procedure or other course of treatment.
Examination of tissue samples taken by biopsy, often by the above-mentioned “vacuum assisted large core biopsy sampler” is of particular significance in the diagnosis and treatment of breast cancer which is the most common cancer suffered by women in the U.S.A and elsewhere in the industrially developed world. Proper diagnostic procedures, frequent examination by well known techniques such as “mammography” and prompt subsequent surgical treatment have, however, significantly reduced the mortality rate caused by this form of cancer. For this reason, in the ensuing discussion of the pertinent background art and in the ensuing description the invention will be described as used for marking biopsy sites in human and other mammalian breast, although the invention is suitable for marking biopsy sites in other parts of the human and other mammalian body as well.
Thus, as is known, when an abnormal mass in the breast is found by physical examination or mammography a biopsy procedure follows almost invariably. The nature of the biopsy procedure depends on several factors. Generally speaking, if a solid mass or lesion in the breast is large enough to be palpable (i.e., felt by probing with the fingertips) then a tissue specimen can be removed from the mass by a variety of techniques, including but not limited to open surgical biopsy or a technique known as Fine Needle Aspiration Biopsy (FNAB). In open surgical biopsy, an incision is made and a quantity of tissue is removed from the mass for subsequent histopathological examination. In the FNAB procedure, a small sample of cells is aspirated from the mass through a needle and the aspirated cells are then subjected to cytological examination.
If a solid mass of the breast is small and non-palpable (e.g., the type typically discovered through mammography), a relatively new biopsy procedure known as “stereotactic needle biopsy” may be used. In performing a stereotactic needle biopsy of a breast, the patient lies on a special biopsy table with her breast compressed between the plates of a mammography apparatus and two separate digital x-rays are taken from two slightly different points of view. A computer calculates the exact position of the lesion with X and Y coordinates as well as depth of the lesion within the breast. Thereafter, a mechanical stereotactic apparatus is programed with the coordinates and depth information calculated by the computer, and such apparatus is used to precisely advance the biopsy needle into the small lesion. Usually at least five separate biopsy specimens are obtained from locations around the small lesion as well as one from the center of the lesion.
After the biopsy sample is taken, it may take several days or even a week before the results of the examination of the sample are obtained, and still longer before an appropriate treatment decision is reached. If the decision involves surgery it is clearly important for the surgeon to find the location in the breast from where the tumor tissue has been taken in the biopsy procedure, so that the entire tumor and possibly surrounding healthy tissue can be removed. For example, the particular treatment plan for a given patient may require the surgeon to remove the tumor tissue and 1 centimeter of the tissue surrounding the tumor. A co-pending application for United States Letters Patent by the same inventors discloses markers which are particularly well adapted for marking biopsy sites in the human breast, and which markers remain detectable by X-ray, ultrasound or some other detection technique only for a given time period (i.e. for 6 months) and slowly disappear thereafter, for example by absorption into the body. The purpose of such markers is to facilitate the surgical procedure that is performed while the marker is still detectable. The disappearance of the marker after a longer period of time may be advantageous to avoid obscuring or interfering with follow-up studies or further mammography or other imaging studies.
In connection with the background art the following specific printed art is mentioned. U.S. Pat. Nos. 2,192,270 and 5,147,307 describe visually discernible markers that are applied externally to the patient's skin. Radiographically (X-ray) detectable tissue markers (e.g., clips or staples) that are attached to tissue adjacent to the site from which the biopsy specimen has been removed, are described in International Patent Publication No. WO 98/06346. Radiographically visible markers (e.g. marker wires) that may be introduced into the biopsy site and are inserted through the biopsy needle after a tissue sample is removed and which are thereafter allowed to remain protruding from the patient's body, are also described in WO 98/06346. However, due to the consistency of breast tissue and the fact that these biopsy site markers are typically introduced while the breast is still compressed between the mammography plates, these biopsy markers of the prior art may become attached to adjacent bands of connective tissue that do not remain at the specific location of the biopsy after the breast has been decompressed and removed from the mammography apparatus, and may suffer from additional disadvantages as well.
Thus, there is still a need in the art for of biopsy site markers that are deliverable into the cavity created by removal of the biopsy specimen and not into tissue that is located outside of that biopsy cavity, and which will not migrate from the biopsy cavity even when the breast tissue is moved, manipulated or decompressed. Moreover, such desired markers should remain detectable at the biopsy site i.e. within the biopsy cavity for an indefinite time period, and still should not interfere with imaging of the biopsy site and adjacent tissues at a later point of time, and most importantly should be readily distinguishable in the various imaging procedures from lines of calcifications which frequently are signs for a developing malignancy. The present invention provides such permanent biopsy site markers as well as apparatus and method for delivering such markers into the biopsy cavity.